MICROTHAMBEMA TENUIS N. GEN., N. SP. (ISOPODA ASELLOTA ...

138 J. A. BIRSTE1N
All three families are closely connected with the family Janiridae, though each
of them by different characters. The family Thambematidae is similar to the
Janiridae by their prehensile peraeopod 1 but differs by the dactyli of all other
peraeopods. Contrariwise the Microjaniridae and the Microparaselhdae, resembling
the Janiridae in respect to the structure of dactyli of peraeopods 2 to 7, differ by
their peraeopod 1 being not prehensile. However, the Microparaselhdae differ from
most Janiridae by the structure of mandibular molar process.
According to Menzies (1956) the new family Echinothambemidae, which he
has described from the Puerto-Rico trench, is near to the Thambematidae, It seems
to me, however, that these families are distant from one another, since in the
Echinothambemidae the posterior thoracic somites are fused together and with
both the abdominal somites; they have no mandibular palp and are characterised
by a peculiar structure 0f the first antenna, single-segmented uropods, etc. The
Thambematid'ie oy their characteristic features are nearer to the Janiridae, Microparasellidae
and Microjaniridae than to the Echinothambemidae.
The well-developed free first abdominal somite, inherent to the Thambematidae,
Microparasellidae and Microjaniridae, distinguishing them from the Janiridae,
can be considered a primitive character, indicative of a dose relation between
these three families. It is highly probable that they have retained this feature,
associated with acute bending of the body, owing to their mode of life in capillaries
between soil particles. We are as yet entirely ignorant of the mode of life
of the abyssal Thambematidae, but it may be inferred from their body form
similar to that of the Microparasellidae and Microjaniridae, that they too live in
capillaries between soil particles.
DISTRIBUTION
The families Microparasellidae and Microjaniridae in the sense suggested in
this paper have a similar distribution. Representatives of both families are known
from interstitial fresh and marine shallow waters.
Among the three genera of the family Microparasellidae the genus Mkroparasellus
with its two species occurs solely in fresh subterranean waters of Jugoslavia
and North Africa. The genus Microebaron (identical with the genus Duslenia
Levi — see Birstein, 1952 and Chappuis and Delamare, 1954) included 10 species
from fresh interstitial waters of Jugoslavia, Rumania, Hungary and Corsica and
3 marine shallow water psammophile species found in the English Channel off •
Plymouth and on the Mediterranean coasts of Italy and France (Chappuis and
Delamare, 1954; Spooner, 1959; Karaman, 1959). And finally the genus Ange-
Hera, with two species, occurs in fresh, brackish and marine interstitial waters of
South France and Italy and in marine interstitial waters of India (Schulz, 1954;
Gnanamuthu, 1954).
The family Microjaniridae includes four genera. Among them, the monotypic
genera Mkropera and Caerianiropsis are recorded from marine shallow waters